Electric lamp



A. SITTEL ELECTRIC LAMP April 4, 1939.

Filed Aug. 25,' 1937 Fig. Z.

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Patented Apr. 4, 1939 ELECTRIC LAMP Alfred Sittel, Fichtenau, kreis Germany, assignor to General pany, a corporation of New York Application August 25,

in Germany 3 Claims.

My invention relates to electric lamps and similar devices comprising a bulb having an electric energy translation element sealed therein, and more particularly to stems for such devices.

Stems for electric lamps as made at the present time comprise a flared glass stem tube having a portion fused and compressed around portions of lead-in wires. Although such stems are highly satisfactory for ordinary lamps, they sometimes l@ develop cracks when used in high intensity lamps carrying comparatively heavy current such as lamps used for vehicles, for projection purposes and for sound nlm purposes, due to the fact that the bulb and the internal parts of the lamps be- 5 come very hot during operation. This is particularly the case when the lamp is subjected to intensive vibrations, for instance when the iarnp is used in vehicles.

One of the objects of my invention is to provide a stem for electric lamps and simiiar devices which is not subject to cracking when carrying heavy current loads or when subjected to intensive vibrations.

According to my invention, the above disadvantages are avoided by making the stem tubes of a ceramic material. Such stem tubes are not only more resistant to heat and to impacts than ordinary glass stems, but since theyalso have a considerably higher insulating value at high tem- D peratures, there is less danger of electrolysis.. Further features Vand advantages of my invention will appear from the following detailed description of a species thereof.

In the drawing, Fig. 1 is an elevation, partly S in .cross section, of a gas-:killed incandescent search-light lamp having a stem tube made in accordance with my invention; Fig. 2 is a' cross-, section, at an enlarged scale, of the stem tube; and Fig. 3 is a plan view thereof.

i Referring to the drawing, the lamp comprises a gas-filled bulb 2 having a neck portion l to which the iiared outer edge 3 of a stem tube 4 is sealed. The stem tube 4 consists of a ceramic material which can be hermetically sealed to glass g without forming stresses, for example a mixture of approximately 50% titanium oxide and 50% magnesium oxide. The stem tube 4, as shown in Fig. 3, is provided with four longitudinal holes 5, 6, 1, 8 at its transversely closed inner end. 'Ihe center hole 5 serves for evacuation and for the introduction of gas and the integral exhaust tube portion communicating therewith is closed ofi" at its outer end by the sealed residue 9 of a glass exhaust tube extension 9'. Three heavy inner lead-in wires I0, Il and I2 extend into Niederbarnim, Electric Com- 1937, Serial No. 160,850

October 3, 1936 the openings t', 'l and 8 shoe shaped filament and suppor t a main horsei3 and a linear auxiliary iilament it. The said lead-in wires may be made of` nickel, a nickel alloy,

The main filament i3 is secured tungsten or molybdenum.

to the leads i I and i2 so that it symmetrically intersects the axis of the bulb 2 and is at the focus of an asso- -ciated reflector when the lamp i s in use. The

auxiliary filament l d is secured to the bent ends of the leads i@ and i2 and is located in front of the focus of the associated reector when the lamp is in use. A cap or shield l5 is mounted below the said nlament ifi on the leads IU and it.

The

said shield iii may also be made of ceramic material or of metal if it is insulated from one of the said leads.

The thin seal portions of the three lead-in Wires itl, il, i2 are hermetically sealed in the holes ii, l, t by means of coatings i6 of a vitreous temperature that the coatings i 6 sealed to the stem tube.

are fused and The stem tube will not be deformed because the ceramic material of which it ismade does not soften ture of 1,000 C.

below a tempera- The outer leads Iii', Il', I2' may be made of copper and extend tothe contacts of the base which is not shown. The lamp may of course be provided with only one filament or with more than two filaments, and the filaments and the bulb may have any desired shape. The invention is also applicable to other types of devices such as electric discharge lamps.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electrical device comprising a vitreous bulb having an electric-energy translation element sealed therein, a stem of non-vitreous ceramic material comprising a stem tube having a ared outer end sealed to an opening in said bulb and an integral exhaust tube Within said stem tube extending longitudinally thereof, the inner end of said stem being transversely closed lexcept as to a plurality of lon gitudinally extending openings therethrough one of which communicates with said exhaust tube, lead-in Wires extending through the other of said openings and being hermetically sealed therein ous material, and means hermetic outer end of said exhaust tube.

by fused vitreally sealing the 2. In an electrical device comprising a vitreous bulb having an electric energy translation element sealed therein. a stem of non-vitreous ceramic material comprising a stem tube having a flared outer end sealed to an opening in said bulb and an integral exhaust tube within said stem tube extending longitudinally thereof, the inner end of said stem being transversely closed except as to a plurality of longitudinally extending openings therethrough one of which communicates with said exhaust tube, lead-in wires extending through the other of said openings and being hermetically sealed therein by fused vitreous material, andmeans consisting of the residue of a vitreous exhaust tube extension hermetically sealing the outer end of said exhaust tube.

3. In an electrical device comprising a vitreous bulb having an electric energy translation element sealed therein, a stem of non-vitreous ce` ramic material consisting of a mixture of the oxides of titanium and magnesium suitable for sealing to glass and comprising a stem tube having a ilared outer end sealed to an opening in said bulb and an integral exhaust tube within said stem tube extending longitudinally thereof, the inner end of said stern being transversely closed except as to a plurality of longitudinally extending openings therethrough one of which communicates with said exhaust tube, lead-in wires extending through the other of said openings and being hermetically sealed therein by fused vitreous material, and means hermetically sealing the outer end of said exhaust tube.

ALFRED SII'I'EL. 

